Dear All
I had a discussion with a colleague recently as to the use of NNT or NNH
when the outcome is harm ie wound infection. I have not been able to find
any "rules" on when to use NNT as opposed to NNH, so have had to apporach
their use deductively. Briefly, I believe that NNT should be used when the
ARR is positive (and therefore is a reduction in the incidence of harmful
outcome). On the other hand NNH should be used when the ARR is negative
(actually an absolute risk increase, and therefore there is an increase in
the incidence of harmful outcome).
However, my colleague has pointed out that semantically this makes litle
sense; where the outcome is harm, then NNH should be used. Where the outcome
is beneficial, then NNT should be used. Essentially this would mean when
there was risk increase, NNH would always be used, but when there was risk
reduction, either NNH or NNT would be used depending on whether or not the
outcome was harm, thus enhancing the terms' communicative meaning. I can
see that this might make more sense from a user's point of view and would
welcome the list's views on this.
regards
Andrew Jull
Clinical Nurse Consultant
Auckland Hospital
NEW ZEALAND
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